Effect of mixing on dynamic mechanical properties of ternary blends of carbon black, polypropylene, and ethylene-vinyl acetate copolymers

Abstract

The objective of this study was to investigate the effect of mixing on dynamic mechanical properties of ternary blends of carbon black (CB), ethylene-vinyl acetate copolymer (EVA) and polypropylene (PP). PP/EVA/CB blends were made by compounding a 70/30 wt% EVA/CB blend with PP to maintain a constant ratio between EVA and CB, using a Brabender twin screw extruder. Three blends with CB concentration 3, 5 and 7.5 wt% were studied in a dynamic rheometer. Both dynamic moduli and dynamic viscosity increased when the concentration of EVA/CB increased. The storage modulus and loss modulus of 5 and 7.5 wt% CB blends increased with the increasing number of passes in extrusion. The ratio of increase diminished when the frequency of the dynamic test increased. Multiple passes in the extruder decreased the phase size of the blends and accounted for the change of modulus. Frequency dependency was explained as the result of the slippage between the interface of EVA/CB and PP phases.